Tornadoes

As the severe weather season approaches, North Carolina Emergency Management and the National Weather Service want you to be prepared for tornadoes and severe thunderstorms. Take some time during tornado safety week to make a tornado plan for your family, friends and co-workers. Planning ahead will lower the chance of injury or even death in the event a tornado strikes.

Tornadoes can occur with little or no warning. You will have only a short time to make life-or-death decisions. It is important to know the basics of tornado safety so that you can survive should one strike.

Listen to the radio, local television, weather channel or a National Oceanic and Atmospheric Administration (NOAA) radio for information.

Don’t wait until a warning is issued to begin planning how you will respond. Take responsibility for your safety and plan now.

Have a plan. Meet with household members to discuss how to respond to an approaching tornado. Hold tornado drills. Learn how to turn off the water, gas and electricity at the main switches.

The safest place to be during a tornado is underground in a basement or storm cellar. If you have no basement, go to an inner hallway or smaller inner room without windows, such as a bathroom or closet. Go to the center of the room. Try to find something sturdy you can get under and hold onto to protect you from flying debris and/or a collapsed roof. Use your arms to protect your head and neck.

Mobile homes are particularly vulnerable to damage from high winds. Residents, even those who live in mobile homes with tie-downs, should seek safe shelter when a tornado threatens. Go to a prearranged shelter when the weather turns bad. If you live in a mobile home park, talk to management about the availability of a nearby shelter. If no shelter is available, go outside and lie on the ground, if possible in a ditch or depression. Use your arms to protect your head and neck and wait for the storm to pass. While waiting, be alert for the flash floods that sometimes accompany tornadoes.

Never try to outrun a tornado in a car. A tornado can toss cars and trucks around like toys. If you see a funnel cloud or hear a tornado warning issued, get out of your vehicle and find safe shelter. If no shelter is available, lie down in a low area using your arms to cover the back of your head and neck. Be sure to stay alert for flooding.

Be alert to what is happening outside. Here are some tornado danger signs:

If there is a watch or warning posted, falling hail should be considered as a real danger sign.

An approaching cloud of debris can mark the location of a tornado, even if a funnel is not visible.

Before a tornado hits, the wind may die down and the air may become very still.

Tornadoes generally occur near the trailing edge of a thunderstorm. It is not uncommon to see clear, sunlit skies behind a tornado.

Even though their times on Earth are short-lived, tornadoes are nature’s most violent and destructive atmospheric phenomenon. The are capable of toppling buildings, lifting and rolling mobile homes and automobiles, and hurling people, animals, trees, and debris hundreds of yards in the ait. The United States has the dubious distinction of having the most severe, damaging tornadoes of any country in the world. The combination of moisture, cold air, and strong winds east of the Rockies provide the perfect ingredients for tornado formation. North Carolina is included in the tornado-prone area.

Producing the deafening sounds of roaring jet engines or rumbling freight trains, destructive tornadoes usually travel in a path averaging nine miles in length, ten yards wide, and at speeds ranging from 35 to 45 miles per hour. The can generate violently rotating columns of air with speeds up to 300 miles per hour.

In North Carolina, the most deadly tornado outbreak this century occured on the night of March 28, 1984. The twisters left 44 dead, more than 800 injured, and over $105 million worth of damages.

A tornado usually appears as a funnel-shaped cloud, spinning in a counter-clockwise direction, and extending from the base of a large thundercloud to the ground. They vary from grey to black in color and can bee seen when the air column contains condensation, surface dust, or debris.

Some exceptionally large tornadoes lack the classic funnel shape and may appear as large, turbulent clouds or rain shafts near the ground. Occasionally, two or more tornadoes occur simultaneously, extending from the same thunderstorm.

It is not uncommon for major tornado outbreaks or families of tornadoes to occur during the same period, causing widespread damage over an extensive area, including several states.

One of the nation’s worst recorded “outbreaks” — called the “Deadly Half Dozen” — the Super Outbreak of April 3-4, 1974, touched down in North Carolina.

Identified as Tornado #148, the last of the family touched down near Baton in Caldwell County. Tornado #121 claimed lives when it struck near Murphy. The storms claimed 315 people as they roared through 13 states.

Strong winds, heavy rain, and especially large hail often precede a tornado and are clear warning signs of impending tornado formation. Large hail stones — 3/4 inches or greater in diameter — are often found in that portion of a thunderstorm mass where strong to violent tornadoes are most likely to occur.

Most significant tornadoes come from the southwest and move in a northeasterly direction. They are unpredictable and erratic in behavior — stationary one moment, and then moving very, very quickly the next. Even though rare, tornado “pathway speeds” of up to 70 miles per hour have been reported.

Through the combined action of stron rotary winds and the impact and speed of airborne debris, tornadoes quickly become a destructive and deadly force. Until recently, it was believed that the drop of atmospheric pressure caused buildings to explode or collapse. The actual cause is the force of the tornado winds pushing the outward wall inward, resulting in the roof being lifted up and the remaining walls falling outward.

What is the most deadly threat of a tornado? Flying debris. The fact is that most tornado-related deaths are caused by head injuries from flying debris. Sticks, glass, roofing materials, lawn furniture, and other similar materials have become dealy missles when driven by the force of a tornado’s strond winds. Demonstrating the incredible strength of a tornadoe’s wind force, in 1931, a tornado in Minnesota carried an 88 ton railroad coach and its 117 passengers 80 feet through the air and dropped them in a ditch. In 1975, a tornado in Mississippi carried a home freezer through the air for more than a mile.

Tornado Facts:

Tornadoes are violently rotating columns of air extending from severe thunderstorms to the ground.

Tornadoes are usually preceded by very heavy rain and, possibly, hail. If hail falls from a thunderstorm, it is an indication that the storm has large amounts of energy and may be severe. In general, the larger the hailstones, the more potential for damaging thunderstorm winds and/or tornadoes.

The most violent tornadoes are capable of tremendous destruction, with wind speeds of 250 m.p.h. or more!

An average tornado damage path is one to two miles long, but can be in excess of one mile wide and 50 miles long.

Widths vary considerably during a single tornado, from less than ten yards to more than a mile, but are typically about 50 yards wide.

The average tornado moves from southwest to northeast, though tornadoes have been known to move in any direction.

The average forward speed of a tornado is 30 m.p.h., but vary from nearly stationary to more than 70 m.p.h.

Tornadoes can occur throughout the year; however, the peak season in North Carolina is March through May.

Tornadoes are most likely to occur between 3 p.m. and 7 p.m., but have been known to occur at all hours of the day or night.

National Weather Service (NWS) Offices in Raleigh, Morehead City and Wilmington, NC; Blacksburg and Wakefield, VA; Greenville-Spartanburg, SC; and Morristown, TN provide warnings for North Carolina.

The NWS is now using Doppler Radar to sense air movement within thunderstorms. Early detection of increasing rotation aloft within a thunderstorm can allow time for lifesaving warnings before the tornado forms.

Tornado MythsThere are dozens of myths and stories about tornadoes. Unfortunately, not having the facts and acting on bad information can have deadly consequences. Here is a short list of popular myths about tornadoes, and the correct information (courtesy of NOAA and Wikipedia):

Using Highway Overpasses as ShelterMyth: Highway overpasses are adequate shelter if a tornado approaches while you are on a road.

The Truth: Sensational footage taken by a television crew hiding from a tornado under an overpass during the 1991 Andover, Kansas Tornado Outbreak helped to convince some that bridges are good shelters when a tornado is nearby. The members of the television crew (and several other travelers) survived by huddling high underneath the bridge and bracing themselves against support columns while a weak tornado appeared to pass directly over the bridge.

In reality, when directly hit by tornadoes, the confined spaces beneath overpasses increase the speed of the winds due to the Venturi effect, and thus make them potentially less safe (somewhat like being in a windtunnel). In the case of the Andover tornado footage, it was discovered that the tornado did not pass directly over the bridge, but instead over the ground slightly south of the bridge and camera crew, exposing them to much weaker winds.

Tornado Behavior Myth: I don’t have to worry about skinny tornadoes, only the fat or big ones are strong.

The Truth: A lethal myth. In the first place all tornadoes are dangerous, and should never be dissmissed as “not powerful”. Secondly, although large tornadoes are generally more powerful, this is not always the case. There have been many instances where “classic” funnels (normal size) or even skinny funnels were deadly F-4 or F-5 tornadoes, where-as a large 1/2 mile wide “wedge” tornado (which make up a lot of F-4 or F-5’s) might be an F-3. So the width of a tornado is not a good indicator of how powerful it is, and all tornadoes should be taken very seriously.

Myth: Tornadoes don’t happen at night.

The Truth: Not only is this a fatal myth, but tornadoes at night are among the most dangerous of all, since most people are asleep and don’t hear the warnings when they happen. It is true that the vast majority of tornadoes happen in the daytime, generally in the late afternoon during the high heating of the day, but tornadoes can and do happen at anytime of the day or night.

Myth: Twisters are attracted to mobile homes and/or trailer parks.

The Truth: Trailer parks consist of low-cost mobile homes with less structural integrity than traditional houses. A weak storm that leaves little damage to well-built structures might devastate a trailer park. Mobile homes do not attract tornadoes; they are just more susceptible to damage from them.

Myth: Tornadoes cannot form near rivers or cross them, Tornadoes cannot follow terrain into steep valleys, Tornadoes cannot travel over steep hills or mountains. Some places like cities and downtown areas are safe from tornadoes.

The Truth: Tornadoes can, do, and have struck all of the above. Among the many tornadoes that have crossed rivers is the most deadly tornado in US History: the Tri-State Tornado, which crossed the Mississippi River and strengthened into an F5. All of the tornadoes from the Super Outbreak that struck in NC struck in the mountains, including an F4 near Murphy, NC that crossed a 3,000 ft. ridge. Finally, there have been many tornadoes that struck downtown areas, including the F5 that devastated Moore, OK in 1999.

Home Safety in a Tornado Myth: Most tornado damage is due to the low pressure in the tornado causing the house to explode. Opening your windows or doors while a tornado approaches will equalize atmospheric pressure and help prevent property damage.

The Truth: Since windows are typically the most fragile external feature of a house, they are in more danger from flying debris. Opening them during an active tornado wastes time and effort that could be spent on other, more useful protective measures. Homes do not “explode” when hit by a tornado, though it often appears so. Commonly, a tornado will break the windows first, allowing strong winds to enter the home. These winds may then push on the underside of the roof upwards, blowing it off. Without the roof, the walls lose structural support and will often fall outwards. Observing the wreckage after the collapse may give the impression the house was pushed apart from the inside. Other ways a house may be perceived to have been “blown apart” is from the winds pushing up against the roof where it meets the walls, ripping the roof off, and causing the walls to collapse.

Flying debris or wind from a tornado will break the windows anyway, so opening them only wastes valuable time and is even counterproductive to the soundness of the structure. It is the debris and wind that breaks windows, not the difference in pressure.

As a note, this also applies to homes or structures that are hit by a hurricane. Studies from the National Hurricane Center suggest that closed containers do not explode during high wind scenarios. But rather, an opening, such as a broken window, will allow the hurricane force winds to enter a room and subsequently destroy an entire building.

Myth: During a tornado, the southwest corner of a building is the safest.

The Truth: An unfortunately fatal belief, and for a long time it was considered sound advice but without any proof of safety compared to any other parts of a building. After the increase in tornado research during the turn of the millennium, the US National Weather Service has now adopted the advice that the central-most-room on the lowest level of a structure is the safest, with centrally-located rooms in an underground level being far safer than any above-ground location. In reality, a tornado can hit any part of a building thereby making any part of the exterior subject to damage from rapidly changing winds.

Tornadoes are classified according to wind speed and damage.

The Enhanced Fujita ScaleThe Enhanced Fujita Scale (EF Scale) is scheduled to go into practice on Feb 1, 2007. The scale represents better engineering studies on different types of structures and how those structures are designed.

(F6+) Inconceivable Tornado (319 – 379 m.p.h.) These winds are very unlikely. The small area of damage they might produce would probably not be recognizable along with the mess produced by F4 and F5 wind that would surround the F6 winds. Missiles, such as cars and refrigerators would do serious secondary damage that could not be directly identified as F6 damage. If this level is ever achieved, evidence for it might only be found in some manner of ground swirl pattern, for it may never be identifiable through engineering studies There is, by definition, no such thing as an F6 tornado.

Since 1950, North Carolina has averaged 14 tornadoes and two tornado-related fatalities each year. 1998 was a record tornado year in North Carolina with 66 confirmed tornadoes through the end of November. The previous record year was 1996, when 51 tornadoes hit the state.

In North Carolina, F0 and F1 tornadoes account for 77% of all tornadoes, but only 9% of all damages, 3% of all fatalities, and 14% of all injuries. As the storms’ strength increases, so does their ability to produce death and damage. F4 tornadoes account for a mere 2.5% of all NC tornadoes, but have produced 52% of all damage costs, 40% of all tornado fatalities, and 44% of tornado injuries.Some of North Carolina’s Tornadoes

Enigma Outbreak: An early recorded outbreak that occurred on February 19 and 20, 1884. An estimated 60+ tornadoes killed between 178 and 1,200 people. In North Carolina, 23 were killed near Rockingham when an F4 tornado struck. Total damages for this outbreak were between $3 and 4 million ($65-87 million in 2008 dollars, which is impressive considering how rural the US was in 1884).

Cordele-Greensboro Outbreak: 14 killed – 144 injured near Greensboro when an F4 tornado struck near downtown Greensboro, NC, carving a line that somewhat follows High Point Road towards Bennett College, and causing $22 million in damage.

1984 Carolinas Tornado Outbreak: March 28, 1984…. an odd outbreak that produced more F4 tornadoes than F0’s, F1’s, F2’s, and F3’s. A total of 24 tornadoes – including 7 F4’s, roared through North and South Carolina. The Bennettsville, SC area was hit by 3 F4’s within a short time. 57 people died (42 in North Carolina) during this outbreak that cost $578 million ($1.15 billion in 2008 dollars).

November 1988 Outbreaks: November 28 tornado in Raleigh killed 4 – 156 injured in 9 counties with $77 million in damages

May 1989 Tornado Outbreak: May 5-6, 1989….. 5 killed and 159 injured as tornadoes strike 22 counties, including Alamance; damages were estimated at $102 million

Palm Sunday Outbreak of 1994: 3/27/1994…. Series of storms (Palm Sunday Storms) roared out of Alabama, spawning numerous tornadoes. Forty-four people were killed over the Southeast. Nineteen at a church in Piedmont, Alabama. Two persons died in North Carolina. Estimated $20 million in damages. Forty counties involved, including Alamance County.

Gainesville-Stonevill Outbreak: March 20, 1998…. 12 tornadoes touched down from Georgia to Virginia, 10 of them in North Carolina. One F3 tornado hit the town of Stoneville, killing 2 and injuring several. Damages from that storm alone were estimated at $34 million.

Mid-May 2008 Outbreak: Three sperate outbreaks of tornadoes occurred during May 2008. The second sequence affected North Carolina with 11 confirmed tornadoes.

Alamance County TornadoesThe following list is compiled from various sources:

Cordele-Greensboro Outbreak: The same outbreak that killed 14 in Greensboro also produced an F2 tornado that killed 1 and injured 4 just north of Mebane. This is the strongest Alamance County on record and the only fatal tornado.

March 19, 1975: An early morning F1 tornado strikes northeast Alamance County and injures 1.

July 21, 1977: An F1 tornado causes $250,000 in damage near Snow Camp.

May 26, 1983: A brief F1 touchdown near Alamance causes $25,000 in damage.

May 1989 Tornado Outbreak: On May 5, 1989, this series of storms produces F1 damage in western Burlington and Elon.

Palm Sunday Outbreak of 1994: 3/27/1994. The massive outbreak produces a brief F0 touchdown in the far southwest section of the county.

March 4, 2008: An F0 storm produces $150,000 in damage in Union Ridge.

Good practices for both schools and residents can be found in the press release below:

North Carolina Emergency Management and the National Weather Service (NWS) urge all schools to develop plans and conduct drills to cope with tornadoes. Tornado drills require different actions than fire drills. Here are some items to consider:

Remember that the NWS issues a tornado WATCH when the possibility of tornadoes exists; and a tornado WARNING when a tornado has been sighted or indicated on radar. Remember, tornadoes can form suddenly and there may not be time for a Tornado Warning before a twister strikes. Teachers and students should know the difference between a Watch and a Warning.

School officials at the state and county level should have a plan for rapid dissemination of tornado Watches and Warnings to every school in the system – either by radio or telephone.

Each school should be inspected and tornado shelter acres designated. Schools with basements should use these as shelters. Schools without basements should use ground floor interior hallways that are not parallel to the tornado’s path, which is usually from the southwest. Never use gymnasiums, auditoriums or other rooms with wide, free-span roofs. Teachers and students should know their designated shelter areas.

School administrators should establish procedures governing use or non-use of school buses during tornado Watches and Warnings. Generally speaking, school buses should continue operating during tornado Watches, but not during tornado Warnings. School buses are easily rolled by tornado winds.

During a tornado Watch, specific teachers or other school staff members should be designated to monitor commercial radio or TV for tornado Warnings, even if the school has a NOAA Weather Radio tone-alert system. Weather spotters also should keep on eye on the sky for dark, rolling clouds, hail, driving rain, or a sudden increase in wind, in addition to the telltale funnel. Tornadoes are often obscured by precipitation or darkness. Other public agencies also report tornado sightings.

A special alarm system should be designated to indicate a tornado has been sighted and is approaching. A backup alarm system should be planned for use if electrical power fails – perhaps a battery-powered bullhorn, an inexpensive hand-cranked siren, or even an old-fashioned hand-swung bell.

Specific teachers should be assigned to round up children on playgrounds or other outdoor areas during a tornado Warning. Otherwise, they might be overlooked.

Children in schoolrooms of weak construction – such as portable or temporary classrooms – should be escorted to sturdier buildings or to predetermined ditches, culverts, or ravines, and instructed to lie face down, hands over head. Most tornado deaths are caused by head injuries.

When children are assembled in school basements or interior hallways during a tornado drill or Warning when the danger is imminent, they should be instructed to respond to a specific command to assume protective posture, facing interior walls. Such a command might be “everybody down! Crouch on elbows and knees! Hands over back of head!” It is essential that this command be instantly understood and obeyed. Illustrations showing the protective position should be posted on bulletin boards.

If a school bus is caught in the open when a tornado is approaching, the children should be escorted to a nearby ditch or ravine and made to lie face down, hands over head. They should be far enough away so the bus cannot topple on them. School-bus drivers should be regularly drilled in tornado procedures.

School district officials planning new buildings or additions should keep tornadoes in mind when setting construction standards.

Tornado WATCH

IT MEANS there is a chance of dangerous weather with damaging winds. Be on the lookout for danger signs listed below and be ready to move quickly to safety if the Warning Signal is given.

Tornado WARNING

IT MEANS a tornado has been sighted. Go at once to the area listed below. If you see or hear the tornado coming, do not wait for the Warning Signal – go to your shelter area if there is time; if not, curl up on the floor and protect yourself as the boy in the picture is doing. If a tornado comes while you are on the school bus, get away from the bus and into a nearby ditch or ravine. Lie down, hands over head.